The Boone County Medical Examiner’s Office determined the man had died prior to the house fire and the cause of his death was poisoning from ethylene glycol, often used as an antifreeze, the news station reported.

Citing a probable cause statement, KMIZ News reported Murray allegedly started the blaze, then left the home and went to a McDonald’s with her 11-year-old son and their dogs. The woman then returned to the burning home but didn’t go inside to look for her husband due to the amount of smoke.

However, investigators said they found a McDonald’s sandwich on the kitchen counter at the house.

Murray worked part-time as a nurse at the Jefferson City Correctional Facility, where she had a “romantic relationship” with an inmate, who is serving a life sentence for killing an elderly man in 2000.

In recorded phone calls at the facility, Murray told the inmate she wanted to divorce her husband. Following the fire, she allegedly told the prisoner they could get married because her husband was dead and “out of the picture,” according to KMIZ News.